1. Field of the Invention
The present invention relates to a bearing structure of a turbo charger.
2. Description of Related Art
As a bearing structure of a turbo charger, as indicated in Japanese Patent Application Publication No. 2005-133635 (JP 2005-133635 A), for example, a bearing structure in which a semi-float bearing is mounted in its bearing housing to support a rotary shaft of the turbo charger has been known. This semi-float bearing is formed cylindrically. The above-described rotary shaft passes through the semi-float bearing and has a slinger wall which is opposed to an end face in the axial direction of the semi-float bearing.
Oil is supplied to each of between the outer circumferential face of the semi-float bearing and the bearing housing and between the inner circumferential face of the semi-float bearing and the rotary shaft. Then, the supply of oil between the outer circumferential face of the semi-float bearing and the bearing housing results in formation of oil layer between the outer circumferential face of the semi-float bearing and the bearing housing so as to suppress vibration of the same bearing (rotary shaft). On the other hand, the oil supplied between the inner circumferential face of the semi-float bearing and the rotary shaft lubricates a gap between the inner circumferential face of the semi-float bearing and the rotary shaft and at the same time, cools the same portion.
In the above-mentioned bearing structure of the turbo charger, the oil supplied between the inner circumferential face of the semi-float bearing and the rotary shaft flows to the outer circumferential face side of the same semi-float bearing via a gap between the end face in the axial direction of the semi-float bearing and the slinger wall of the rotary shaft. If the oil flow increases, it becomes difficult to retain oil between the inner circumferential face of the semi-float bearing and the rotary shaft, thereby the cooling efficiency by the oil being reduced.
If the direction of the oil flow cannot be controlled when the oil supplied between the inner circumferential face of the semi-float bearing and the rotary shaft flows to the outer circumferential face side of the semi-float bearing via the gap between the above-mentioned end face and the aforementioned slinger wall, a following problem may occur. That is, the oil which flows out to the outer circumferential face of the semi-float bearing via the gap between the above-mentioned end face and the aforementioned slinger wall may flow to a wheel fixed to the end portion in the axial direction of the rotary shaft of the turbo charger so that there is a fear that it may leak out to the same wheel side.